130 THE PHYSIOLOGY OF REPRODUCTION 



of ooition in rabbits which have given birth to young just previously, 

 and Iwanorf, 1 in confirmation of this statement, records experiments 

 in which pregnancy was induced in rabbits by the artificial injection 

 of seminal Huid shortly after parturition (cf. p. 102). 



In the mouse, 2 the rat, 3 and the guinea-pig, 4 ovulation occurs 

 spontaneously during " heat," and generally, if not invariably, during 

 oestrus."' 



In the dog ovulation takes place independently of coition after 

 external bleeding has been going on for some days, or when it is 

 almost or quite over ; in other words, it occurs during oestrus and 

 not during the procestrum, or at any rate not during the early stages 

 of the procnstrum.' 5 It is probable that the sow also ovulates during 

 oestrus and not during the procestrum, since it is stated that sows are 

 most successfully served on the second or third day of "heat." 7 

 Coition, if it occurs earlier, is frequently not followed by conception. 8 

 From Hausmann's description it would seem that ovulation does 

 not take place prior to coition, but this conclusion is certainly 

 incorrect. 9 



In the ferret ovulation occurs during oestrus, but postponement 

 of coition may bring about the degeneration of the ripe follicles, 

 since they do not usually discharge spontaneously. 10 



Robinson, 11 who has made a very close study of the phenomenon of 

 maturation and ovulation in the ferret, states that the time intervening 

 between insemination and follicular rupture may vary from 30 hours 

 to 93i hours. 



1 Iwanotf, "La Fonction des Vesicles sciiiinales et de la Glande prostalique," 

 Jvtir. </ /'//*. // <! rth. < //,<., v.il. ii., 1900. 



s Sobotta, /-. n't. See also Kirkham, " Ovulation in Mammals, etc.," Hiol. 



/;'".. vol. \\iii., MUM. 



3 Tafani, " Li rY-.-..n<lati"ii .-t la Segmentation studiees dans les (Kufs des 

 Rattes," Jr-7,. //,//. ,/, /;//.. x,,l. ii., 1889. cf. Kirkham, loc. c& 



1 Kuliaschkin, /<. n't. Sc-e also Loeb (L.), "The Cyclic Changes in the Ovary 

 of tin- (iuin-a-j)i^, I: Jon,: of Mor/i/i.. vol. xxii., 1911. 



rding to Smith (H. P.) the ovarian cycle in mice varies from sixteen to 

 nineteen days (I'n*: A, .!/<"/. No. .V> , .!//<//. /,'<,-//-,/, vol. xi., 1917). 



According to Long and Quisno, rat? ovulate every ten days (Science, vol. xliv 

 1916). 



' Marshall and .lolly. "( 'oiiti ilmtions to the Physiology of Mammalian 

 Reproduction: Part I. Tin- <K>tions ( yrle in the Dog," J'/n'/. '/'/'///#., B., 



Vol. rx.-viii., liMCp. 



7 See Mackenzie and Mai shall, "<)n Ovariotomy in Sows," Jour, of A <///>. 

 f, vol. i\-., I91i. According to Corner and Ausbaugh, ovulation may 

 occur before the third day of h'-at, .1 not /,'.<"/v/, vol. xii., 1917, 



' Walla.:.- (I!.), l-'ann 'Life Xt<>,-i- ,,f <, ',-,;, t /!,-;>. ,,'. ith Edition, London, 1907. 



I Hausinami. t'.-lvrdic K<-n>i>ni "n<l Ei-tftehung de* wakren weiblichen Eies. 

 etc., Hanov.-r, I^JH. 



" Marshall, "Th. * lustrous Cycle in the Common Ferret," ({uar. Jour. J///T. 

 I. xlviii., I'.HiJ. 



II Robinson, "Tin- KOI -mation, IJupturc, and Closure of Ovarian Follicles 

 in Ferrets, etc.," Tr<n.*. /,W Soc. />//.. vol. Hi., 1918. 



